In the first three parts of this series, I discussed three critical factors to consider when choosing a screen for your home entertainment room: size and viewing distance, screen gain, and aspect ratio. In this, the final instalment of the series, I'll finish the discussion off with details on acoustically transparent screens, using specialty paint for your screening wall, and other alternatives worth considering.
What About "Acoustically Transparent" Screens?
First of all, "acoustically transparent" is a misnomer. Once you put something, anything, in front of your speakers, it can never be truly acoustically transparent. It's more like acoustically "translucent." The question is, how transparent is the acoustic translucence of the screen?
"Acoustically transparent" screens tend to be more expensive than regular flat screens. The most affordable ones are made of micro perforated vinyl with a density of around 200 holes per square inch. This type of screen will result in drop off starting at around 100Hz and tend to cliff down at around 1kHz. I'm strongly against this type of screen because I find that the end result is detrimental to the audio quality. Furthermore, these types of micro-perforated screens tend to create moiré when coupled with digital projectors, require a minimum viewing distance of approximately 12-feet, and the speakers behind the screen can not be installed closer than 12-inches away.
The second type of "acoustically transparent" is the woven-material screen. They have perforation-pitch of anywhere between 500 to 1,500 holes per square inch. The higher the number, the closer it is to being a truly "acoustically transparent" screen. Also with the higher perforation-pitch number, the closer you can sit to the screen and the closer the speakers can be located behind the screen. At 1,500 holes per square inch, you can sit as close as 8-feet without being able to see any perforation (even if you try very hard) and you can install the speakers as close as 1-inch behind the screen without creating any ripple on the screen. Also, at 1,500 holes per square inch, the frequency roll-off starts at around 4kHz and is only noticeable at frequencies higher than 14kHz. This is approximately the roll-off frequency of most adults' hearing frequency curve anyway, thus making the roll-off undetectable.
Regardless, image quality will suffer with either moiré effect, softening of the image, loss of light, or all of these combined. On the other hand, having the dialogue exactly coming from where the mouth of the character in the movie is located is an experience to behold. In this case, choose your poison. Better video quality but having the dialogue coming out from below the screen, or better sonic imaging but with compromised overall sound and image.
Screen Goo set up in the home theatre showroom at Just HiFi in Kingston, ON
What About a Bare Wall or Screen Goo?
Other options include using a bare wall or painting using a "special" paint called "Screen Goo" (or its variants).. Will it have a good result? It depends. A bare wall is a definite no-no, in my opinion. With special screen paint? Well...
First, you would have to make sure the wall is 100% flat to ensure a perfect viewing experience, which is virtually impossible. Second, if you use "Screen Goo" or any other kind of specialty paint, you will need to be able to have the exact thickness of paint coats in order to give an equally reflective surface. This can be a very time-consuming task.
If you absolutely need to save money, at the very least, just get the cheapest stretched vinyl screen you can find. They can be purchased for around $100.
Now, I have seen a good image from a painted wall using specialty paint. But the homeowners noted having paid about $300 in paint, a roller, and other materials, plus about a day's worth of labour to get everything perfect. I have neither the skill nor the patience to do that, so I can't recommend the option. I also wouldn't pair my $10,000 projector with anything but an industry-reference screen. But for DIY-ers who might enjoy this challenge and project, it may be something worth considering.
At the end of the day, it's not the price of the screen that determines the quality, but it's the pairing. Once you get the pairing correct, you'll enjoy the screen for at least a decade before you need to replace it, or in the case of paint, re-paint.
Of course, there are more aspects that need to be considered when opting for the paint alternative, including the paint colours of your walls and ceiling, carpet, door - the list goes on. But that's where a long-in-the-tooth Level 3 ISF and/or THX certified independent AV consultant can help. So if you're ready to buy and still have questions after reading this series, consult with someone local in your area, and find the right projection screen for you.